This invention relates generally to antibodies which specifically bind to hepatitis C virus (HCV), and more specifically, relates to a panel of novel hybridoma cells lines which secrete monoclonal antibodies which specifically bind to the putative HCV protein E2/NS1, and methods for using these monoclonal antibodies.
Descriptions of hepatitis diseases causing jaundice and icterus have been known to man since antiquity. Viral hepatitis is now known to include a group of viral agents with distinctive viral organization protein structure and mode of replication, causing hepatitis with different degrees of severity of hepatic damage through different routes of transmission. Acute viral hepatitis is clinically diagnosed by well-defined patient symptoms including jaundice, hepatic tenderness and an elevated level of liver transaminases such as aspartate transaminase and alanine transaminase.
Serological assays currently are employed to further distinguish between hepatitis-A and hepatitis-B. Non-A non-B Hepatitis (NANBH) is a term first used in 1975 that described cases of post-transfusion hepatitis not caused by either hepatitis A virus or hepatitis B virus. Feinstone et al., New Engl. J. Med. 292: 454-457 (1975). The diagnosis of NANBH has been made primarily by means of exclusion on the basis of serological analysis for the presence of hepatitis A and hepatitis B. NANBH is responsible for about 90% of the cases of post-transfusion hepatitis. Hollinger et al. in N. R. Rose et al., eds., Manual of Clinical Immunology, American Society for Microbiology, Washington, D.C., 558-572 (1986).
Attempts to identify the NANBH virus by virtue of genomic similarity to one of the known hepatitis viruses have failed thus far, suggesting that NANBH virus has a distinctive genomic organization and structure. Fowler et al., J. Med. Virol, 12: 205-213 (1983), and Weiner et al., J. Med. Virol, 21: 239-247 (1987). Progress in developing assays to detect antibodies specific for NANBH has been hampered by difficulties encountered in identifying antigens associated with the virus. Wands et al., U.S. Pat. No. 4,870,076; Wands et al., Proc. Natl. Acad. Sci. 83: 6608-6612 (1986); Ohori et al., J. Med. Virol. 12: 161-178 (1983); Bradley et al., Proc. Natl. Acad. Sci. 84: 6277-6281 (1987); Akatsuka et al., J. Med. Virol. 20: 43-56 (1986).
In May of 1988, a collaborative effort of Chiron Corporation with the Centers for Disease Control resulted in the identification of a putative NANB agent, hepatitis C virus (HCV). M. Houghton et al. cloned and expressed in E. coli a NANB agent obtained from the infectious plasma of a chimp. Kuo et al., Science 244: 359-361 (1989); Choo et al., Science 244: 362-364 (1989). cDNA (copy DNA) sequences from HCV were identified which encode antigens that react immunologically with antibodies present in a majority of the patients clinically diagnosed with NANBH. Based on the information available and on the molecular structure of HCV, the genetic makeup of the virus consists of single stranded linear RNA (positive strand) of molecular weight approximately 9.5 kb, and possessing one continuous translational open reading frame. J. A. Cuthbert, Amer. J. Med. Sci. 299: 346-355 (1990). It is a small enveloped virus resembling the Flaviviruses. Investigators have made attempts to identify the NANB agent by ultrastructural changes in hepatocytes in infected individuals. H. Gupta, Liver 8: 111-115 (1988 ); D. W. Bradley J. Virol. Methods 10: 307-319 (1985). Similar ultrastructural changes in hepatocytes as well as PCR amplified HCV RNA sequences have been detected in NANBH patients as well as in chimps experimentally infected with infectious HCV plasma. T. Shimizu et al., Proc. Natl. Acad. Sci. 87: 6441-6444 (1990).
Considerable serological evidence has been found to implicate HCV as the etiological agent for post-transfusion NANBH. H. Alter et al., N. Eng. J. Med. 321: 1494-1500 (1989); Estaben et al., The Lancet: August 5: 294-296 (1989); C. Van Der Poel et al., The Lancet August 5: 297-298 (1989); G. Sbolli, J. Med. Virol. 30: 230-232 (1990); M. Makris et al., The Lancet 335: 1117-1119 (1990). Although the detection of HCV antibodies eliminates 70 to 80% of NANBH infected blood from the blood supply system, the antibodies apparently are readily detected during the chronic state of the disease, while only 60% of the samples from the acute NANBH stage are HCV antibody positive. H. Alter et al., New Eng. J. Med. 321: 1994-1500 (1989). These data clearly indicated the need for the identification of additional HCV proteins for efficient serodiagnosis of HCV infection. Following the cloning and expression of structural protein CORE and 33C, second generation antibody assays have been developed which employ HCV CORE and 33C proteins in addition to C-100 for the detection of antibodies to HCV in NANB patients. Although the second generation assays have significantly increased the sensitivity of detection, the prolonged interval between exposure to HCV and antibody detection, and the lack of adequate information regarding the profile of immune response to various structural and non-structural proteins raises questions regarding the infectious state of the patient in the antibody negative phase during NANBH infection. Therefore, there is a need for the development of assay systems to identify acute infection to HCV and the presence of HCV.